Roof supports for mine workings



y 1968 K. M. GROETSCHEL 3,383,866

ROOF SUPPORTS FOR MINE WORKINGS Filed Dec. 3, 1965 4 Sheets-Sheet 1 hag/42 '///J// Inventor: KowL maria. G'voeiscbeL 2 y 21, 1968 K. M. GROETSCHEL 3,383,866

ROOF SUPPORTS FOR MINE WORKINGS Filed Dec. 5, 1965 4 Sheets-Sheet 5 529 mg we l8! m ISZC |5|0 W9 |8l 2 I82 Fig.9 150p \nvencor: I

KavL Mona. GvoetscbcL Hiiovnetss United States Patent 3,383,866 ROOF SUPPORTS FOR MINE WORKINGS Karl M. Groetschel, 44 Stolzestrasse,

463 Bochum, Germany Filed Dec. 3, 1965, Ser. No. 511,511

Claims priority, application Great Britain, Dec. 7, 1964,

49,739/64; Aug. 3, 1965, 33,045/ 65 12 Claims. (Cl. 6145) ABSTRACT OF THE DISCLOSURE A self-advancing roof support for supporting the roof of a mine working and including at least one base element having laterally spaced, generally parallel, side members, means rigidly connecting the side members to each other adjacent their forward and rearward ends, the side members and connecting means defining a medial longitudinally extending slot, the support further including a roof-engaging superstructure including an outer part having laterally-spaced, longitudinally extending roof bars rigid along their lengths, means connecting the roof bars rigidly with each other and defining together therewith an upwardly open, longitudinally extending channel overlying the slot, the support also including an inner part composed of an elongated, longitudinally rigid beam disposed in the channel, two props each extending between a respective one of the side members at its rearward end and a respective one of the roof bars to support the latter, at least one prop extending between the base element at its forward end and the roof bars for supporting the latter, and two longitudinally-spaced props, one disposed adjacent the forward end of the base element and the other disposed in the slot at a point spaced rearwardly from the forward end of the slot, the latter props supporting the beam, the arrangement finally including traction means for advancing the beam and the outer part of the superstructure alternately.

This invention relates to self-advancing roof supports primarily for use in underground mine workings and of the kind comprising a base, a plurality of power-operated extensible props on said base, a roof-engaging superstructure carried by the props at their upper ends, and traction means for advancing the support. Such roof supports are hereinafter referred to as being of the kind specified.

The invention has been developed primarily in relation to a self-advancing roof support of the kind specifiedsuitable for use in what is known as mechanised long wall coal mining. In this method coal-getting machinery is traversed horizontally along a coal face and coal thus removed from the face is discharged or deflected onto a conveyor which extends along the coal face. The roof of the mine working extending over the top of the coalgetting machinery and conveyor, and in a direction away from the coal face, requires to be supported as the coal face advances with removal of coal therefrom.

Advancement of roof supports of the kind specified, while preserving the requisite degree of safety for operating personnel, is one of the major problems which exists relative to such supports.

Roof supports of the kind specified ordinarily have a roof-engaging superstructure which projects forwardly beyond the base of the support so as to be capable of supporting the roof of a mine working over the top of coalgetting machinery and the conveyor, such roof portion being situated in the immediate vicinity of the coal face.

To enable the support to be maintained against the roof, especially when the latter has faults in the form of vertical or upwardly extending cracks, fissures or planes of weakness extending generally parallel to the coal face, it is desirable that at least part of the roof-engaging super- 3,383,866 Patented May 21, 1968 ICC? structure shall remain in supporting relation to the roof while another part of such superstructure is advanced to move beneath portions of the roof newly exposed after passage of the coal-getting machinery.

During operation of the support operating personnel are ordinarily stationed in a region beneath that part of the superstructure overlying the base.

The main object of the present invention is to provide a support which meets this requirement or more nearly meets it, than is the case for any previously available form of roof support of the kind specified.

A specific further object of the invention is to provide at all times, whether the support be stationary or undergoing advancement, continuous support in a longitudinally extending zone above the base of the support by way of a part of the superstructure supported by at least two longitudinally spaced props.

According to the invention a self-advancing roof support for supporting the roof of a mine working comprises a base including at least one base element having laterally spaced, generally parallel, side members rigid throughout their lengths, means rigidly connecting said side members with each other adjacent to their forward and rearward ends, said side members and connecting means defining a medial longitudinally extending slot, a roof-engaging superstructure including an outer part having laterally spaced, longitudinally extending, roof bars rigid along their lengths, means connecting said roof bars rigidly with each other and in combination therewith defining an upwardly open, longitudinally extending, channel overlying said slot, an inner part comprising an elongated, longitudinally rigid, beam disposed in said channel, a plurality of power-operated extensible props including two props each extending between a respective one of said side members at its rearward end and a respective one of said roof bars to support the latter, at least one prop extending between said base element at its forward end and said roof bars to support the latter, two longitudinally spaced props, one being disposed adjacent to the forward end of said base element and one in said slot at a position spaced rearwardly from the forward end of said slot, these props supporting said beam, and traction means for advancing said beam and outer part of said superstructure alternately.

A further roof condition which is sometimes encountered is that some times the load exerted by the roof is not at right angles to the roof surface, that is to say directly" vertically, but applies a horizontal component of force to the roof-engaging superstructure usually in a direction away from the coal face so that the supporting props tend to be deflected angularly in planes longitudinally of the support.

A further object of the invention is to provide a support which will withstand loading of this kind.

The invention thus further provides a self-advancing roof support for supporting the roof of a mine working comprising a base, a plurality of power-operated extensible props on said base, a roof-engaging superstructure carried by the props at their upper ends, traction means for advancing the support, bracing means connected between said base and said superstructure at respective positions thereon spaced from each other longitudinally of the support to resist loads applied to the superstructure from the roof and which would otherwise tend to produce angular deflection of the props in a direction longitudinally of the support.

The invention will now be described, by way of example, with reference to certain embodiments thereof illustrated in the accompanying drawings wherein:

FIGURE 1 is a view in side elevation showing a first embodiment of the invention utilised in a method of mechanised long wall coal mining;

FIGURE 2 is a plan view of the same embodiment, a

portion of the rear part of the superstructure being broken away to show the supporting arrangement therefor;

FIGURE 3 is a plan view of the base of the support on the line 33 of FIGURE 6 showing also certain components of the traction means;

FIGURE 4 is a fragmentary view in cross-section on the line 44 of FIGURE 1 showing the suspension arrangements for the prop constituting the auxiliary device;

FIGURE 5 is a fragmentary cross-sectional view on an enlarged scale on the line 55 of FIGURE 2;

FIGURE 6 is a fragmentary cross-sectional view on an enlarged scale on the line 66 of FIGURE 3;

FIGURE 7 is a plan view on an enlarged scale of a portion of the base;

FIGURE 8 is a view similar to FIGURE 1 of a second embodiment of the invention;

FIGURE 9 is a plan view of the base and certain components of the traction means of the embodiment of FIGURE 8;

FIGURE 10 is a fragmentary view on an enlarged scale and in cross-section on the line 1ti-19 of FIG- URE 9;

FIGURE 11 is a view in side elevation of a third embodiment of the invention; and

FIGURE 12 is a plan view of the base and certain components of the traction means of the embodiment of FIGURE 11.

In FIGURE 1 the support is shown in use for mechanised long wall coal mining in a mine Working in which the coal face is indicated at 10 and the floor and roof of the working at 11 and 12 respectively. A coal-getting machine 13 is traversed along the coal face to cut coal therefrom which is discharged onto a conveyor 14 of the known flexible armoured type which is capable of being moved or snaked section by section successively along its length towards the coal face as the latter advances with the extraction of coal therefrom.

The support itself comprises a superstructure including a rear part 15 and a fore part 16. The rear part is formed as a frame including laterally spaced, longitudinally extending, roof bars 17 rigidly connected to each other by forward and rearward cross members 18 and 19. Both of the cross members are disposed below the roof bars 17 so as to lie in downwardly offset or cranked relation thereto at positions between the roof bars so that collectively the roof bars and the cross members afford an open-ended, upwardly presented, channel in which a rear portion 26 of the fore part 16 of the superstructure lies.

The roof bars 17 may each be formed from two roof bar sections of box-shape in vertical cross-section welded to each other along projecting flanges presented by the top and bottom walls of the section which protrude somewhat beyond laterally spaced vertical webs of the section.

The outer roof bar sections have welded to their forward ends housings 21 of bifurcated form. Forepoling arms forming extensions of the rear part of the superstructure, as indicated at 22, may optionally be pivoted between the limbs of these housings 21, such forepoling arms being capable of being elevated and lowered under power by means of wedge elements 23, protruding through slots 24 in the housings and operated by respective pistons at opposite ends of a hydraulic cylinder 25. The forepoling arms may, if desired, be equipped with raised roof-engaging pads 26.

The fore part of the superstructure 16 is in the form of an elongated beam and comprises two laterally spaced roof bar sections 27, preferably of box-shape in vertical cross-section, connected to each other at intervals along their lengths by cross members 28, 29 and 35), these latter fitting between inwardly projecting flanges formed by the top and bottom walls of the roof bar sections which project laterally of the vertical webs thereof.

At the outer sides of the roof bar sections the latter may have welded thereto longitudinally extending guide pads 27a, the outer faces of which are flush with, or slightly proud of, the laterally projecting flanges.

One of the cross members 29 is of elongated form and has a length somewhat exceeding the length of the advancement step which it is required to impart to the forepart of the superstructure, as hereinafter described.

As seen more particularly in FIGURE 5, the member 29 incorporates two block-like portions 31 and 32 at opposite ends having a height such as to fit closely between the upper and lower flanges 33 and 34 of the associated roof bar sections, and connected by a plate-like portion 35 abutting and welded to the upper flange 33. The plate-like portion 35 presents a smooth downwardly directed guide surface 36 with which is engaged a sliding shoe 37 incorporating a domed seating 38 at its lower side for reception of a prop head as hereinafter described.

At its forward end the fore part of the superstructure 16 may optionally be provided with a raised roof-engaging pad 39 pivotally connected by a horizontal pin 40 to the forward end portion of the elongated beam.

The provision of such pad ensures the existence of a raised roof-engaging face at the forward end of the elongated beam and this ensures that the latter applies support to the roof in this region despite irregularities in the roof, the intervening portion of the elongated beam between the pad 39 and the rear end of the beam thus bearing hollow with respect to the roof. In this hollow bearing zone the roof is supported by the rear part 15 of the superstructure.

The rear part of the superstructure is supported at its rearward end by two laterally spaced hydraulic props of which one is seen in FIGURE 1 at 41. At their upper ends the prop heads which may be of domed form engage in downwardly presented concave seatings afforded by members 42 welded or otherwise secured to the undersides of respective roof bars 17.

At its forward end the rear part of the superstructure is supported by one of the sections of a single multisection prop 43 disposed centrally of the support. This hydraulic prop incorporates three or more prop sections of which all (other than the smallest transverse crosssection) are of tubular form open at one end and closed at the other end, the sections being assembled with each other in telescoping relation collectively to form a laterally rigid strut extensible by hydraulic fluid admitted to two separate chambers defined by successive sections and bounded longitudinally by the closed ends thereof. One of the terminal sections, namely that of largest cross-section 44, is situated at the lower end and is supported from the base of the support, as hereinafter described. The section of next largest cross-section forms a piston with respect to the section 44 and is equipped at its upper end with a load-bearing element 45 in the form of a generally oval-shaped yoke having laterally projecting lugs 45 carrying upwardly extending posts 47 engaging in seatings afforded by members 48 similar to the members 42 welded or otherwise secured to the undersides of the roof bars 17.

The fore part of the superstructure 16 is supported by the innermost section 49 of the multi-section prop 43. The innermost section 49 together with the next largest section of the prop form an independent removable piston and cylinder unit or prop which, as hereinafter described, can be removed from the centre of the remaining sections of the multi-section prop and separately employed at a position remote from the latter if desired.

The upper end of the prop section 49 is of domed form and, as seen in FIGURE 5, engages in the seating 38 of the shoe 37.

The props so far described are all carried by a single base element 50. This base is a fabricated structure. It comprises two laterally spaced elongated side members in the form of chambers 51 of generally rectangular shape in transverse cross-section, each having a top plate 52, a bottom plate 53, and an outer side plate 54 and two laterally spaced inner side plates 83b providing guide passageways 83a. The side plates 83b may be welded to the top and bottom plates 52, 53.

At their rearward ends the chambers 51 incorporate raised parts 51a, the top walls of which are apertured, and fitted with split clamping rings 51b, to provide seatings for the props 41, the lower ends of the props 41 rest on the parts of the bottom plates 53 which have socket members 53a welded to them. At their forward ends, the chambers 51 are connected to a forward central chamber 55 also fabricated from plates and having a top wall 56 formed with an aperture 57 for receiving the multi-section prop 43, downwardly and outwardly sloping side walls 58 and a rear wall 59, all welded to the top plate 52 of the chambers 51, and a vertical front wall. The chamber 55 may also have a bottom wall on which the lower end of the multi-section prop rests. Between the two chambers 51 the base affords a longitudinally extending medial opening in the form of slot 60.

In the slot is disposed a further prop 61 which is seen in FIGURE 1 and the position of which is indicated diagrammatically in broken line in FIGURE 3.

As hereinafter described this prop is required to move along the slot during operation of the support. The innermost side plates of the box-section passageways are parallel to each other, as indicated diagrammatically at 83b (FIGURE 7) but the inner edges 53b of the bottom plates 53 are preferably divergent in a direction from front to rear of the slot. This feature tends to prevent accumulation of loose material from the floor of the mine working between the sides of the prop 62 and the edges 53b, and thereby prevents jamming or obstruction to movement of the prop 62 along the slot. The prop 62 is equipped with a base plate 62a which preferably includes an upwardly inclined leading end portion, such base plate resting directly on the floor of the mine working. The prop 62 is a hydraulic prop and may have the same effective piston area as that afforded by the props 41. At its upper end it engages in the cross member 30 at the rearward end of the elongated beam, which cross member for this purpose is formed with a concave seating 63 for reception of the domed prop head 64. The inner section 65 of this prop has a collar 66 secured, for example clamped, to it beneath which engage the inwardly directed limbs 67 of brackets 68 secured as by welding to the roof bar sections 27 so that a prop is effectively suspended from the fore part of the superstructure.

Means are also provided for raising the lower section of the prop 62 from the ground or at least partially relieving the pressure of its weight on the ground. Such means comprise coiled tension springs 69 extending between anchor elements 70 on the brackets 68 and 71 on the lower section of the prop 62. A steadying bracket 69a is also secured to, and extends downwardly from, the fore part of the superstructure behind the prop 61 to prevent rearward deflection of this prop during its advance along the slot while suspended from the fore part of the superstructure.

The rearward end of the slot 60 is defined by a shield member 72 in the form of an upstanding fabrication secured rigidly to the rearward ends of the chambers 51. The shield member thus comprises inner plates 73 which are welded to the rearward ends of the chambers 51 and an outer plate assembly 74, 74a. The whole structure is reinforced internally by horizontal webs 75 and vertical I-section girders 75a welded to the inner and outer plates. The webs 75 are formed with part-circular recesses 76 of curvature to conform to that of the outer section of the prop 62 which engages these recesses when the prop is disposed at the rear end of the slot 60, as seen in FIG- URES 1 and 3.

Inasmuch as the shield member 72 extends upwardly to a position just beneath the rear part of the superstructure, it serves to prevent roof material which has been allowed to cave or descend in the rear of the support, falling into the laterally extending manway 77 afforded between the base, the rear part of the superstructure, and the props 41 and 43 supporting the latter.

The traction means of the support comprises a part which is disposed in the base of the support. This part includes two double-acting hydraulic rams 78 pivotally connected at their rearward ends to the base, for example to brackets 78a secured to the top and bottom plates 52, 53. The forward end portions of these rams 78 protrude through the open forward ends of the chambers 51 with which are associated closure members 79 preferably formed of a flexible sheet material such as rubber. The closure members 79 are apertured to fit over the traction rams 7 8.

The piston rods of the traction rams are connected by forked terminations 80 and pivot pins 81 to a transverse traction bar 82 to which is fixed a pair of laterally spaced slide bars 83. These slide bars extend into the interior of the box-section guides 83a and have substantial vertical and lateral clearance with respect to the latter so that, if desired, extension of the two traction rams 78 by different amounts can produce controlled advancement of the traction bar along a predetermined path to the left or to the right of a medial longitudinally extending reference axis of the support.

A further part of the traction means is mounted at the level of the superstructure and comprises a hydraulic traction ram 84 pivotally connected at its forward end by means of a pin 85 passing through a forked termination of the ram to a lug on the shoe 37 which, by virtue of its engagement with the head of the prop section 49, remains stationary during advancement of the fore part of the superstructure. The opposite end of the ram .84, for example its piston rod 86, is pivotally connected about a horizontal axis to the cross member 28 which for this purpose has laterally spaced apertured lugs 87 to receive a pivot In the embodiment of the invention illustrated in FIG- URES 8 to 10 parts corresponding functionally to those already described in the embodiment of FIGURES 1 to 7 are designated by like numerals of reference with the prefix 1 and the preceding description is to be deemed to apply thereto.

In this second embodiment one of the major differences is that, instead of mounting all the props on a base comprising a single base element, the base comprises two base elements, a being the rear base element and 1501) being the forward base element.

The forward base element serves as the mounting for the prop 14% supporting the fore part of the superstructure 116. Such forward base element comprises a box or frame 1500 and a base plate 150d which may either be fixed to the box or frame or to the bottom of the prop I43b. The box or frame is formed in its sides with vertically extending slots 150s in which engage lugs 1430 on the lower section of the prop allowing the latter to move vertically relatively to the box or frame and also to tilt angularly to a limited extent within the box or frame.

The latter is provided with an upwardly extending bracket 150 equipped with a pad 150g or rubber or other suitable material which engages the lower section of the prop to transmit tractive effort thereto from the traction means incorporated in the base, namely the hydraulic rams 178.

The thrust which the prop 14317 is capable of exerting, when pressurized to its setting load, may be increased to providing a larger diameter prop section 143d acting as a booster, this section comprising a cylinder and a hollow piston which receives the lower end of the prop section 149a.

The piston rods of the hydraulic rams 178 are connected to brackets 182 which are functionally equivalent to the traction bar 82 of the previous embodiment and which are welded or otherwise secured to the box or frame 150a.

The rear part and the fore part of the superstructure may be generally of the same construction as in the previous embodiment except that the former need not be provided with a part of the traction means, although such could be provided if desired to enable the fore part of the superstructure to be advanced relatively to the prop 149.

To enable the further prop 161, which supports the rear end of the fore part of the superstructure, to move along the slot 169 of the rear base element 150a a connecting element of elongated flexible form, such as a chain or a wire rope, is provided. This connecting element 190 forms a loop, the ends of which are clamped in the apertures of blocks 191 on the brackets 182 by means of set bolts 192. The two limbs of the connecting element 190 which forms a loop lie alongside the lateral boundaries of the slot 160 within the latter and at its rearward end the connecting element passes loosely round the further prop indicated diagrammatically at 161 in FIGURE 9.

In the method of mechanised long wall coal mining the two embodiments hereinbefore described may be operated as follows.

The first embodiment is initially positioned as seen in FIGURE 1 with the fore part of its superstructure in the rearward or retracted position as shown in full lines. For clarity the rear part of the superstructure has been shown in the lowered position but in practice both parts of the superstructure will be in the raised roof-engaging position immediately prior to the transverse past the support of the coal-getting machine 13.

Immediately after passage of the coal-getting machine 13 past the support the fore part of the superstructure may be lowered and the traction ram 84 operated to advance the fore part of the superstructure to the position shown in broken lines. Hydraulic fluid is allowed to flow out of the prop 61 to exhaust so that the springs 69 raise the prop slightly out of contact with the ground or relieve part of the weight and allow the prop to be carried forwardly with the fore part of the superstructure also to the position shown in broken lines.

Thereafter the inner prop of the multi-section prop 43 is repressurised as is also the further prop 61 so that the part of the roof immediately adjacent to the coal face 10 is supported with the minimum of delay after passage of the coal-getting machine.

It is necessary for the coal-getting machine to progress some distance beyond the support before it is possible for the adjacent section of the conveyor 11 to be snaked or advanced towards the coal face, but when the coalgetting machine has cleared this section, this operation can then be effected by pressurising the traction rams 178 to advance the traction bar which is operatively connected to a suitable bracket on the conveyor, as seen at 88.

After advance of the conveyor the props 41 and the outer section of the prop 43 are depressurised to lower the rear part of the superstructure. The inner prop unit is either fully depressurised or partially depressurised to eliminate or reduce the upthrust of the supporting shoe 37 against the guide surface 36 of the cross member 29 of the fore part of the superstructure, but the further prop 61 can remain fully pressurised so that the part of the roof lying immediately above the rear part of the superstructure remains satisfactorily supported.

Pressurisation of the traction rams 78, which are double acting, is now effected to draw up the base and the props 41 and 43, together with the rear part of the superstructure, into a position adjacent to the conveyor as seen in FIGURE 1.

Subsequently the props 41 and both the inner and outer units of the multi-section prop 43 are repressurised to the full value before the next traverse of the coal-getting machine 13.

It will thus be evident that at all times the part of the roof immediately above the rear part of the superstructure is supported by at least one prop which is fully 5 pressurised and consequently the risk of personnel being injured by roof falls into the manway '77 is materially reduced.

In using the embodiment illustrated in FIGURES 8 to 10 when the superstructure is equipped with the traction ram 184, the sequence of operations is that the fore part 116 of the superstructure may, and preferably would, be advanced relatively to its supporting prop 1435) immediately after passage of the coal-getting machine beyond the support, the supporting prop 14311 (and booster unit 143d if provided) as well as the prop 1631 being depressurised and the prop 16 being carried along the slot 160 by suspension from the rearward end of the fore part of the superstructure. it would be suspended in this case by an arrangement similar to that illustrated in FIGURE 4 including lifting springs for the lower section of the prop, and the fore part of the superstructure would preferably be provided with a steadying bracket as seen in FIGURE 1.

Subsequently when the coal-getting machine has a vanced sufficiently beyond tl e adjacent conveyor section to permit the latter to be snaked towards the coal face, depressurisation or partial depressurisation of the prop 1 13b (and the booster unit 143d if provided) is effected preparatory to extension of the traction rams 178. The forward base element 15th; then advances and, by means of its pusher llfih advances the conveyor section 1E4 towards the coal face.

Thereafter the props 143i) (and the booster unit 143d if provided) are again fully pressurized whilst the props 141 and 143a are depressurised to lower the rear part of the superstructure 117 which is then, together with its base element 159a, drawn up by appropriate pressurisation of the traction rams 178 (double acting).

Where no traction cylinder 18-; is provided in the fore part of the superstructure, props 161, 1431; (and the booster unit 143:! if provided), together with the forward base element 15Gb, are advanced as a whole and in this case movement of the prop 161 along the slot is ensured by the rope or chain 199, it being then unnecessary to provide any means for suspending or for steadying same, and for lifting or raising lower sections of this prop from the ground during its advancement.

In both embodiments the rear portion of the fore part of the superstructure is temporarily supported on cross members such as 18 or 118 at the rear part of the superstructure during its advancement.

It will be understood that any conventional means may be provided for pressurising or setting the props. This may comprise a power-operated hydraulic pump or in some cases a manually operable pump. The setting mode to which each prop is initially pressurised is determined by setting valve means which may be provided on the pump to cause this to blow off or relieve pressure at a predetermined value. Between this valve means and each of the props the appropriate hydraulic supply pipe would be equipped with a non-return valve and between the nonreturn valve and the prop concerned, preferably on the prop itself, would be provided a further relief valve which blows off or opens at a higher pressure than that determined by the relief valve means of the pump.

This allows the props to be pressurised to a higher value (the yield load after they have been set initially and as a consequence of any tendency of the roof to descend. The pump, the various pipes, and the valve means have been omitted from the drawings for the sake of clarity.

In many instances the fore part of the superstructure is preferably so arranged that the arm or portion thereof which extends forwardly of the foremost supporting prop 43 or 143 as the case may be, is shorter than the arm or portion which extends rearwardly thereof so as to enable the supporting thrust developed against the roof immediately adjacent to the coal face to be a higher proportion of the thrust furnished by the prop 43 or 143 than in the case at the rearward end of the fore part of the superstructure.

Whatever disadvantage is inherent in this arrangement through reduced support to the roof abovethe rear part of the superstructure when the latter no longer serves to support this roof (during advancement of the rear part of the superstructure) is overcome by the present invention since the prop 61 or 161 ensures an additional complement of support.

Furthermore, since the fore part of the superstructure is pressed against the roof by two longitudinally spaced props 61 and 43 or 161 and 143 as the case may be, it is more securely held against angular deflection in a plane parallel to the roof than would be the case were it supported only by the forward prop 43 or 143. Consequently when using the support in mine workings which present an inclination along the coal face from one end towards the other, there is less risk of the support as a whole becoming angularly deflected. It will be understood that during advancement of the rear part of the superstructure the latter may be lowered only sufficiently to provide the requisite clearance with respect to the roof and consequently the inner sides of the roof bars 17 can contact guide pads 27a or 127a as the case may be.

Referring now to the embodiment illustrated in FIG- URES 11 and 12, parts thereof corresponding functionally to parts of the previously described embodiments are designated by like numerals of reference with the prefix 2 and the preceding description is applicable thereto.

In this construction the further seating 260 provided in the base 250 is in the form of a circular aperture formed in the top wall of the base which is not slotted medially, the top walls of the two laterally disposed chambers being integrally connected with each other.

The bottom wall of the base need not be apertured in alignment with the aperture which forms the seating 260. In the seating 260 is disposed a prop 241 which supports the rearward end of the superstructure.

The support includes a bracing structure which includes posts 293 preferably each comprising two telescopically assembled sections 294 and 295, the former having a series of holes 296 extending through it and provided with a pin 297 for insertion through one pair of such holes so that the protruding ends rest on the lower section 294 to determine the effective height of the post.

At its upper end each post is connected to a respective bar or girder of a forwardly extending strut assembly which may comprise a laterally spaced pair of bars or girders of box-section or I-section having downwardly inclining lower end portions 298.

The girders 297 are secured at their forward ends to the cross member 218, either by welding or by provision of brackets on the cross member to which the forward end or ends of the girders 297 can be connected by bolts, a similar bolted connection being effected between the rearward ends and the posts 293. It will be evident that the posts 293 are rigidly supported in upright positions in the upstanding chambers 251a at the rearward ends of the base element 250.

The bracing structure comprising the posts and girders 297 resists angular deflection of the props 243 and 241 -which serve to support the superstructure comprising the fore part 216 and rear part 217.

Such angular deflection may occur under certain exceptional conditions of roof load wherein the roof load imposed on the superstructure does not consist wholly of a thrust at right angles to the plane of the roof so that the resultant downward thrust is oblique to the roof surface. Usually when such thrust is present it is directed downwardly and rearwardly, that is to say away from the coal face, and thus tends to cause the superstructure to be displaced rearwardly relatively to the base and the props to tilt in a rearward direction.

What I claim then is:

1. A self-advancing roof support for supporting the roof of a mine working comprising (a) a base having at least one seating adjacent to its forward end and having laterally spaced seatings adjacent to its rearward end,

(b) a plurality of power-operated extensible props disposed in said seatings,

(c) a roof-engaging superstructure carried by said props at their upper ends and including (i) a rear part substantially co-extensive in a direction longitudinally of the base with the forward and rearward ends thereof, and comprising laterally spaced, longitudinally extending roof bars connected by laterally extending cross members adjacent to the ends of the roof bars, the forward cross member at least being offset or cranked downwardly in between the roof bars to define in combination therewith an openended channel presenting an open end forwardly.

(ii) a fore part comprising an elongated beam having its rear portion disposed in said channel and its forward portion projecting forwardly beyond said base, said fore part being supported by one of said props on said base,

(d) a further seating in said base, said further seating being of elongated form and extending longitudinally of said base in a region situated centrally of the width of said base,

(e) a further prop in said elongated seating and supporting said rear portion of said fore part,

(f) traction means for advancing said support.

2. A support according to claim 1 wherein the further prop supporting the rear portion of the fore part of the superstructure is connected thereto by connecting means including means enabling such prop to be lifted or part of its weight borne by suspension from the fore part during advancement of the latter by said traction means.

3. A support according to claim 1 wherein the base comprises forward and rearward base elements connected with each other operatively by one or more hydraulic traction rams for successive advancement of such elements and carrying respective props supporting the forward and rearward parts of the superstructure, and wherein the further prop is operatively connected with the forward base element by a connecting element extending longitudinally of the support.

4. A support according to claim 3 wherein said connecting element is a cable extending longitudinally of said elongated further seating between the forward base element and the further prop.

5. A support according to claim 1 wherein said superstructure further comprises (a) arms extending forwardly of said roof bars, respectively, at the forward ends of the latter,

(b) means connecting said arms to said roof bars for transmitting roof load from said arms to said roof bars.

6. A support according to claim 5 wherein said arms have forward ends situated laterally adjacent the forward end of said beam.

7. A support according to claim 5 wherein said connecting means for connecting said arms to said roof bars, respectively, comprises (a) pivot means about which said arms can be elevated and lowered in substantially vertical longitudinal planes,

(b) power-actuated means for effecting at least said elevating movement.

8. A self-advancing roof support for supporting the roof of a mine working comprising (a) a base including at least one base element having (i) laterally spaced, generally parallel, side members rigid throughout their lengths,

(ii) means rigidly connecting said side members with each other adjacent to their forward and rearward ends,

said side members and connecting means defining a medial, longitudinally extending, slot,

(b) a roof-engaging superstructure including (i) an outer part having laterally spaced longitudinally extending, roof bars rigid along their lengths,

(ii) means connecting said roof bars rigidly with each other and in combination therewith defining an upwardly open, longitudinally extending, channel overlying said slot,

(iii) an inner part comprising an elongated, longitudinally rigid, beam disposed in said channel,

(0) a plurality of power-operated extensible props including (i) two props each extending between a respective one of said side members at its rearward end and a respective one of said roof bars to support the latter.

(ii) at least one prop extending between said base element at its forward end and said roof bars to support the latter,

(iii) two longitudinally spaced props, one being disposed adjacent to the forward end of said base element and one in said slot at a position spaced rearwardly from the forward end of said slots, these props supporting said beam,

(d) traction means for advancing said beam and outer part of said superstructure alternately.

9. A support according to claim 8 wherein (a) said prop in said slot comprises an upper section and a lower section assembled with, and movable telescopically relative to, said upper section,

(b) means are provided for retaining said upper section against downward displacement and separation from said beam,

(c) means are provided for raising said lower section to avoid or reduce drag of said section on the ground underlying said slot during advancement of said prop by said traction means.

It). A support according to claim 9 further including means for steadying said prop in said slot against deflection during advancement along said slot and comprising a steadying member extending downwardly from, and

supported from, said beam, said steadying member engaging said prop at a position spaced downwardly from said beam and over a longitudinally presented face of said prop.

11. A self-advancing roof support for supporting the roof of a mine working comprising (a) a base,

(b) a plurality of power-operated extensible props on said base,

(0) a roof-engaging superstructure carried by the props at their upper ends,

(d) traction means for advancing the support,

(e) bracing means connected between said base and said superstructure at respective positions thereon spaced from each other longitudinally of the support to resist loads applied to the superstructure from the roof and which would otherwise tend to produce angular deflection of the props in a direction longitudinally of the support, said bracing means including a bracing structure of generally dog-leg shape, as seen in side elevation, having one limb rigidly upstanding from said base adjacent to one end thereof, and a further elevated limb extending from the upper end of said upstanding limb toward the opposite end of said base and connected thereat to said superstructure.

12. A support according to claim 11 wherein said bracing means comprises (a) at least one post extending upwardly from said base and rigidly connected thereto to resist angular deflection of the post relative to the base in a direction longitudinally of the support,

(b) a strut member extending generally longitudinally of the support and connected between said superstructure and said post at a position adjacent to the upper end of the latter but spaced downwardly from said superstructure.

References Cited JACDB SHAPIRO, Primary Examiner.

D. J. WILLIAMOWSKY, Examiner. 

